Both have most of the same enemies, save for the bramble.
The Crow (That's not the actual name...) is a harder enemy and, if that route is chosen, it would be your first encounter with an enemy that can dodge.
In the full game, judging by it's sprite description, The Crow will be able to 'steal' items in your inventory.
There are 2 unique bosses on this floor(two for each floor, I belive.) but I've yet to reach it. I'll reply again once I've gotten the names of the 'new' enemies and bosses.
P.S.
There're is one unique item in the bramble, there's probably more but i havent found them yet. It's the ramming sheild. It deals damage for each AP/SP (armor/sheild point) you have, at the cost of you losing half of your AP/SP total.
Now you have a reason to use hercule pivase!!
I would like to add that there is a very slim chance you encounter a special event in the bramble that will allow you to gain an extra 5 HP or heal your health. The Bramble (or at least for me) has been fairly easy to take on mostly due to crabs. they don't do a whole lot of damage and all you have to do is block for those first few rounds and then it's quick from there. BE WARNED sometimes The Bramble will throw 3 hermit crabs and one of those mice at you and that can be hard to take out if you don't wield a proper weapon by then.